That was my first thought but the bullet from the 22 stayed in the can. He tells me they were at a trout stream for opening day and I can't help but think he used a water soaked rock. They can pop open explosively. Had it happen to me while cat fishing on the Fox River in Illinois. Scared the bejesus out of 3 young boys and a couple of middle aged men.

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Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.
--Daniel Webster--